Hydraulic master cylinder assembly



May 4, 1965 E. PAGE 3,181,299 HYDRAULIC MASTER CYLINDER ASSEMBLY FiledSept. 9, 1963 3 Sheets-Sheet 1 43 4| 47 39 44 27 29 37 2| I7 23 I3 49 SI15 I I I i I nventar Attorney;

May 4, 1965 E. PAGE HYDRAULIC MASTER CYLINDER ASSEMBLY Filed Sept. 9,1963 S Sheets-Sheet 2 ////WV//V V In M ERNEST PAGE I nuentor AttorneysMay 4, 1965 v E. PAGE HYDRAULIC MASTER CYLINDER ASSEMBLY 5 Sheets-Sheet3 Filed Sept. 9, 1963 ERNEST PAGE Inventor M2 J n-[km B MfiQJ/KJJQAttorney:

United States Patent 3,181,299 HYDRAULIC MASTER CYLINDER ASfdEMBLYErnest Page, Upminster, Engiand, assignor to Ford Motor Company,Dearborn, Mich, a corporation of Delaware Filed Sept. 9, 1963, Ser. No.307,592 Claims priority, application Great Britain, Nov. 1, 1962,41,290/ 62 8 Claims. (Cl. oil-54.6)

The present invention relates to hydraulic actuating devices. Moreparticularly, this invention concerns master cylinder assemblies of thetype used in motor vehicle clutch and brake systems.

Basically, a master cylinder assembly comprises a cylindrical bore, apiston slidable Within the bore, a pressure outlet from the bore and areservoir communicating with the bore. In one type of master cylinder,sometimes referred to as a low pressure type, the port between thecylinder bore and the reservoir is closed by the piston itself. In aso-called high pressure type, the port is closed by a valve member thatmoves in response to movement of the piston. The present invention isconcerned with the latter type.

In one such master cylinder assembly there is a cylindrical bore havinga closed end with a centrally situated port that communicates with thefluid reservoir. A piston is slidably fitted in the bore so that apressure chamber is formed between the end of the bore and the end ofthe piston. A pressure outlet communicates with the pressure chamber andis connected to the clutch, brake or other mechanism served by themaster cylinder assembly.

A valve member is situated at the depth of the bore and is adapted toseal the port connecting the pressure chamber with the reservoir. Thevalve member is secured to the end of a valve stem that has its oppositeend telescopically received within the piston. A coil spring isinterposed between a valve member retainer at the depth of the bore andthe piston in order to return the piston to its static position.

Means are provided on the valve stem so that the piston will engage thestem to withdraw the valve member away from the port in order to permitreplenishing of fiuid from the reservoir into the pressure chamber.

Owing to manufacturing tolerances in the lengths of the cylinder,piston, valve stem, valve member and other parts, it is difficult toinsure that the piston will engage the end of the valve stem correctlywhen the piston travels to its return position. If the piston engagesthe end of the valve stem too soon on its return stroke, the piston isprevented from reaching its fully returned position and there is,consequently, a gap between the piston and the piston push rod. If thepiston engages the valve stem end too late on its return stroke, thevalve member is not moved into its fully opened position when the pistonreaches its fully returned location.

In accordance'with the present invention, it is a principal object,therefore, to provide a master cylinder of the type discussed in whichmanufacturing tolerances have little or no effect on the free or correctmovement of the piston and valve member.

In one preferred embodiment of the present invention as applied to amaster cylinder assembly of the construction previously described, anelement is in frictional engagement with the outer end of the valve stemand slidable relative thereto. The element is engageable by the pistonso that movement of the piston under the action of the return springmoves the valve stem and the valve member to open the port between thepressure chamber and the reservoir. During assembly of the componentparts, the element is automatically moved along the valve stem to theprecise position required.

The manner in which this automatic adjustment of ice the position of thevalve element is eifected in a preferred embodiment will be describedlater. The many objects and advantages of the present invention willbecome amply apparent from the following description and theaccompanying drawings in which:

FIGURE 1 is an elevational view in section of one embodiment of ahydraulic actuator such as a motor vehicle clutch or brake mastercylinder assembly constructed according to the present invention. Inthis view the piston is shown in a fully actuated position.

FIGURE 2 is a sectional view corresponding to FIG- URE l with the pistonshown in the fully returned position.

FiGURE 3 is a sectional view through a part of the assembly.

Referring now to the drawings for a more detailed understanding of thepresent invention, the master cylinder assembly includes a housing 1having a cylindrical bore 3. The housing 1 also has a reservoir 5 thatcommunicates with the interior of the bore 3 through a port 7. The port7 provides communication between the reservoir 5 and the interior of thebore 3.

A stepped piston 13 is slidably received in the cylindrical bore 3. Thevolume between the end of the piston 13 and the closed end 9 of thecylinder comprises a fluid pressure chamber it). An outlet 11 is incommunication with the pressure chamber and is connected to the clutch,brake or other mechanism that is to be actuated by the master cylinderassembly.

The stepped piston 13 has a wide diameter part 15 that is slidable inthe bore 3 and a narrow diameter part 21 spaced inwardly thereof. A seal17 is fitted about a portion of the piston 13 adjacent to a shoulder 19between the wide and narrow parts 15, 21 of the piston 13. An axial bore23 extends into the piston 13 from the narrow diameter end and has ashoulder 25 at its end. An annular recess 27 is provided on the outersurface of the narrow portion 21.

A cup-shaped return spring retainer 29 fits over the end of the narrowpart 21 and has an integral spring finger 31 that engages the recess 27so that the retainer 29 is held securely in position. The retainer 29has an aperture 33 that overlaps the bore 23.

A stool shape retainer 35 is forced against the closed end 9 of thecylinder 3 by a return spring 37 compressed between the stool 35 and aflange 38 on the retainer 29. The stool 35 has a circular aperture 39whose axis is in alignment with that of the bore 23.

A valve member comprising a mounting portion 41 and a rubber seal 43 iscarried by a valve stem. The valve stem has a wide diameter part 44slidable in the stool aperture 39 and a narrow diameter portion 45 thatextends into the piston bore 23. A valve spring 47 of the Bellevilletype is interposed between the stool 35 and the mounting portion 41 andsurrounds the wide di ameter part 44. The spring 47 forces the valvemember toward the position in which the seal 43 closes the port 7. Theloading of the valve spring 47 is very much less than that of the returnspring 37, for example, a few ounces as compared with several pounds.

A sleeve 4? is mounted on and frictionally engages the narrow diameterpart 45.01? the valve stem. The force of the frictional engagementbetween the sleeve 49 and valve stem portion 45 is considerably greaterthan the force required to compress the Belleville spring 47 but lessthan the force of the return spring 37. The edge of the aperture 33 inthe retainer 29 overlaps the sleeve 49 and the diameter of the sleeve4-9 is smaller than that of the bore 23. A collar 51 fixed to the end ofthe stem portion 45 prevents the sleeve from being removed.

A push rod 53 connectable in a conventional manner with a clutch orbrake actuating pedal engages a recess 55 in the end of the widediameter part 15 of the piston 13. A push rod retaining washer 56 isheld in position at the outer open end of the cylinder 3 by a snap ring57. This same snap ring 57 limits movement of the piston to the right orfully returned position.

To assemble the master cylinder, the components shown in FIGURE 3 arefitted together. The return spring 37 is extended so that one end of thesleeve 49 engages the retainer 29 at the aperture 33 and the other endis engaged by the collar 51. Under these conditions, the sleeve 49 islocated on the extreme end of the valve stem. The components shown inFIGURE 3 are then slid into the cylinder 3 until the stool 35 engagesthe closed end 9 of the cylinder 3. The push rod 53, washer 56 and snapring 57 are then fitted.

After assembly, the piston 13 is pushed by the rod 53 to the full strokeposition shown in FIGURE 1. As the piston is moved to the left, theretainer 29 ceases to engage the sleeve 49 and the valve spring 47 is,consequently, able to move the valve stem 44, 45 to the left so that therubber seal 43 closes the port 47. The narrow diameter portion 45 of thevalve stem and the sleeve 49, owing to the frictional engagement betweenthem, move further into the bore 23. Just before the piston reaches itsleft-hand extreme position in which the retainer 29 engages the widediameter portion 44 of the valve stem, the sleeve 49 contacts theshoulder 25 in the bore 23. The final movement of the piston slides thesleeve 49 to the left along the narrow diameter portion 45 of the valvestem.

When the piston 13 is in its extreme left-hand position (the full strokeposition of FIGURE 1), the distance between the stool 35 and the end ofthe sleeve 49 when the sleeve is in engagement with the shoulder 25 isless than the distance from the stool 35 to the end of the sleeve 49when the piston is in the extreme righthand position'in engagement withthe washer 56 (the fully returned position of FIGURE 2). As the push rod53 is released and the piston moves to the right under the action of thereturn spring 37, the valve spring 47 holds the rubber seal 43 againstthe end 9 of the cylinder 3 to close the port 7 until the edge of theaperture 33 in the retainer 29 engages the sleeve 49. When this occurs,the valve stem 44, 45 is moved to the right to compress the Bellevillespring 47 and open the port 7. After the spring 47 has been compressed,further movement of the valve stem 44, 45 to the right is prevented bythe stool 35. Consequently the retainer 29, since the edge of itsaperture 33 engages the sleeve 49, slides the sleeve 49 along the narrowportion 45 of the valve stem until the push rod 53 abuts against thewasher 56.

The sleeve 49 is now precisely located on the narrow portion 45 of thevalve stem so that movement of the push rod 53 through a distance equalto the distance between the rubber seal 43 and the end 9 of the cylinderresults in the seal 43 closing the port 7. Thus, manufacturingtolerances in the lengths of the cylinder 3, piston 13, valve stem 44,45, stool 53, valve member 43, and other components have no effect onthe travel of the push rod 53 required to close the port 7 between thereservoir and the pressure chamber 10 of cylinder 3.

The master cylinder assembly operates in a substantially conventionalmanner. The initial movement of the push rod 53 results in the ports 7being closed by the seal 43 and further movement forces liquid throughthe outlet 11 to the brake or clutch mechanism. Release of the push rod53 enables the return spring 37 to move the piston 13 to the right toenable liquid for the clutch or brake mechanism to enter the pressurechamber 10. During final movement of the piston 13, just before itengages the washer 56 during the return stroke, the seal 43 moves clearof the end 9 of the cylinder to open the port 7 and thus permit liquidto enter the pressure chamber 10.

Engagement of the sleeve 49 by the shoulder 25 in the piston bore onlyoccurs during initial assembly of 4 the components of FIGURE 3 into thecylinder 3. Normally, the sleeve 49 is axially spaced slightly from theshoulder 25.

The foregoing description presents a presently preferred embodiment ofthis invention. Modifications and alterations may occur to those skilledin the art to come within the scope and spirit of the following claims.

I claim:

1. A hydraulic master cylinder assembly comprising a cylinder borehaving an open end and a closed end, a piston slidable in said bore anddefining a pressure chamber between its end and said closed end, apressure outlet in said bore, a fluid reservoir, a port in said closedend providing communication between said reservoir and said chamber, avalve member movable to open and close said port, said valve memberhaving a portion with an element frictionally engageable therewith andslidable thereon, said element being engageable by said piston when saidpiston is moved toward said open end of said bore so that it unseatssaid valve member.

2. A hydraulic master cylinder assembly comprising a cylinder borehaving an open end and a closed end, a piston slidable in said bore anddefining a pressure chamber between its end and said closed end, apressure outlet in said bore, a fluid reservoir, a port providingcommunication between said reservoir and said chamber, a valve membermovable to open and close said port, said valve member having a portionwith an element frictionally engageable therewith and slidable thereon,said element being engageable by said piston when said piston is movedtoward said open end of said bore so that it unseats said valve member.

3. A hydraulic master cylinder assembly comprising a cylinder borehaving an open end and a closed end, a piston slidable in said bore anddefining a pressure chamber between its end and said closed end, apressure outlet in said bore, a fluid reservoir, a port providingcommunication between said reservoir and said chamber, a valve membermovable to open and close said port, first spring means urging saidvalve member toward a closed position, said valve member having aportion with an element frictionally engageable therewith and slidablethereon, said element being engageable by said piston when said pistonis moved toward said open end of said bore so that it unseats said valvemember.

4. A hydraulic master cylinder assembly comprising a cylinder borehaving an open end and a closed end, a piston slidable in said bore anddefining a pressure chamber between its end and said closed end, apressure outlet in said bore, a fluid reservoir, a port in said closedend providing communication between said reservoir and said chamber, avalve member movable to open and close said port, first spring meansurging said valve member toward a closed position, said valve memberhaving a portion with an element frictionally engageable therewith andslidable thereon, said element being engageable by said piston when saidpiston is moved toward said open end of said bore so that it unseatssaid valve member.

5. A hydraulic master cylinder assembly comprising a cylinder borehaving an open end and a closed end, a piston slidable in said bore anddefining a pressure chamber between its end and said closed end, apressure outlet for said chamber, a fluid reservoir, a port in saidclosed end providing communication between said reservoir and saidchamber, a valve member movable between open and closed positions tocontrol fluid flow through said port, retaining means adapted to limitmovement of said valve member away from said port, a valve stemconnected to said valve member and extending into a bore in said piston,a return spring interposed between said retainer and said piston andurging said piston toward the open end of said bore and urging saidretainer against the closed end of said bore, an element in frictionalengagement with said valve stem and slidable thereon, said element beingengageable by said piston when said piston is moved to the open end ofsaid bore, whereby said valve member is moved to an open position, "heforce required to slide said element on said valve stem being less thanthe force exerted by said return spring.

6. A hydraulic master cylinder assembly comprising a cylinder borehaving an open end and a closed end, a piston slidable in said bore anddefining a pressure chamber between its end and said closed end, apressure outlet for said chamber, a fluid reservoir, a port in saidclosed end providing communication between said reservoir and saidchamber, a valve member movable between open and closed positions tocontrol fluid flow through said port, retaining means adapted to limitmovement of said valve member away from said port, a valve stemconnected to said valve member and extending into a bore in said piston,first spring means interposed between said retainer and said valvemember urging said valve member toward a position to close said port, anelement in frictional engagement with said valve stem and slidablethereon, said element being engageable by said piston when said pistonis moved to the open end of said bore whereby said valve member is movedto an open position against the force of said first spring means, theforce required to slide said element on said valve stem being greaterthan the force exerted by said first spring means.

7. A hydraulic master cylinder assembly comprising a cylinder borehaving an open end and a closed end, a piston slidable in said bore anddefining a pressure chamber between its end and said closed end, apressure outlet for said chamber, a fluid reservoir, a port in saidclosed end providing communication between said reservoir and saidchamber, a valve member movable between open and closed positions tocontrol fluid flow through said port, retaining means,

adapted to limit movement of said valve member away from said port, avalve stem connected to said valve member and extending into a bore insaid piston, first spring means interposed between said retainer andsaid valve member urging said valve member toward a position to closesaid port, an element in frictional engage- 6 ment with said valve stemand slidable thereon, said element being engageable by said piston whensaid piston is moved to the open end of said bore whereby said valvemember is moved to an open position.

8. A hydraulic master cylinder assembly comprising a cylinder borehaving an open end and a closed end, a piston slidable in said bore anddefining a pressure chamber between its end and said closed end, apressure outlet for said chamber, a fluid reservoir, a port in saidclosed end providing communication between said reservoir and saidchamber, a valve member movable between open and closed positions tocontrol fluid flow through said port, retaining means adapted to limitmovement of said valve member away from said port, a valve stemconnected to said valve member and extending into a bore in said piston,first spring means interposed between said retainer and said valvemember urging said valve member towards a position to close said port, areturn spring interposed between said retainer and said piston andurging said piston toward the open end of said bore and urging saidretainer against the closed end of said bore, an element in frictionalengagement with said valve stem and slidable thereon, said element beingengageable by said piston when said piston is moved to the open end ofsaid bore whereby said valve member is moved to an open position againstthe force of said first spring means, the force required to slide saidelement on said valve stem being greater than the force exerted by saidfirst spring means but less than the force exerted by said returnspring.

References Cited by the Examiner UNITED STATES PATENTS 2,332,301 10/43Cox -545 X FOREIGN PATENTS 716,008 9/54 Great Britain. 859,911 1/61Great Britain.

JULIUS E. WEST, Primary Examiner.

EDGAR W. GEOGHEGAN, Examiner.

1. A HYDRAULIC MASTER CYLINDER ASSEMBLY COMPRISING A CYLINDER BOREHAVING AN OPEN END AND A CLOSE END, A PISTON SLIDABLE IN SAID BORE ANDDEFINING A PRESSURE CHAMBER BETWEEN ITS END AND SAID CLOSED END, APRESSURE OUTLET IN SAID BORE, A FLUID RESERVOIR, A PORT IN SAID CLOSEDEND PROVIDING COMMUNICATION BETWEEN SAID RESERVOIR AND SAID CHAMBER, AVALVE MEMBER MOVABLE TO OPEN AND CLOSE SAID PORT, SAID VALVE MEMBERHAVING A PORTION WITH AN ELEMENT FRICTIONALLY ENGAGEABLE THEREWITH ANDSLIDABLE THEREON, SAID ELEMENT BEING ENGAGEABLE BY SAID PISTON WHEN SAIDPISTON IS MOVED TOWARD SAID OPEN END OF SAID BORE SO THAT IT UNSEATSSAID VALVE MEMBER.